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Answers to Frequently Asked Rose Questions

News Article

by Richard Jauron, Department of Horticulture

Roses are one of the most beautiful plants in the home landscape. While roses are attractive, they do require good care. Answers to several frequently asked questions on rose care and maintenance are provided below.

Q. How often should I water my roses?

A. Modern roses, such as hybrid teas, floribundas, and grandifloras, require watering during hot, dry weather. The frequency depends upon weather conditions and soil type. In most gardens, a deep soaking every 7 to 10 days during dry weather is sufficient. Soak the soil to a depth of 8 to 12 inches. If possible, apply the water directly to the soil around each plant. Overhead watering wets the foliage and increases disease problems. If overhead watering is unavoidable, morning is the best time to water roses. Morning applications allow the foliage to dry quickly.

An excellent way to conserve soil moisture is by mulching. Possible mulches include wood chips, shredded bark, pine needles, and cocoa bean hulls. Spread 2 to 4 inches of mulch around each rose or over the entire bed. Mulches also help to control weeds.

Q. How often should I fertilize my roses?

A. To encourage vigorous growth and abundant bloom, hybrid tea, grandiflora, and floribunda roses should be fertilized three times a year. The first application should be made in early spring immediately after pruning. Apply the second fertilizer application during the first bloom period. The third application should be made in mid to late July. Do not fertilize after July 31. Later fertilization will produce succulent new growth, which may not harden sufficiently before winter. An all-purpose garden fertilizer, such as 10-10-10 or 5-10-5, should produce excellent results. Sprinkle 1/4 cup of fertilizer around each plant per application. .

Q. What is the proper way to deadhead roses?

A. Deadheading or the removal of faded flowers is done to encourage additional bloom on hybrid tea and other repeat-flowering roses. Hybrid tea roses usually have one or two 3-leaflet leaves immediately below the flower. Next (lower down on the stem) are two or more 5-leaflet leaves. The deadheading procedure is slightly different for newly planted and established roses. During their first growing season, it's usually recommended that the spent flower be removed above the uppermost 3-leaflet leaf. Removal of a larger percentage of the rose's foliage reduces the plant's ability to manufacture food and slows growth. When deadheading established roses, the stem may be cut back to a 5-leaflet leaf. Retain at least two 5-leaflet leaves on each shoot. Use sharp tools (hand shears or knife) to remove faded flowers. Cut about 1/4 inch above an outward facing bud and leaflet with the cut made parallel to the angle of the leaflet.

Q. My hybrid tea rose grows vigorously, but doesn't bloom. Why?

A. Hybrid tea roses are propagated by budding. A single bud is removed from the desired variety and inserted onto a hardy rootstock. The bud union (the knob-like swelling at the base of the canes) is sensitive to extreme cold. If little or no winter protection is provided, the canes may die back to the bud union. New growth originating from below the bud union is from the rootstock portion of the plant. Growth from the rootstock is extremely vigorous, but usually doesn't bloom. Non-blooming plants should be dug up and discarded.

Q. How can I control blackspot on my roses?

A. Blackspot is a common fungal disease of roses. Symptoms of blackspot are circular black spots on the leaves. Infected leaves turn yellow and drop prematurely. Initially, symptoms develop on the lower leaves and gradually move upward. By late summer, severely infected plants may be nearly defoliated.

The blackspot fungus overwinters on fallen leaves and infected canes. Spores are splashed on to newly emerging foliage in spring. Blackspot development is favored by warm (75 F), wet weather.

A combination of cultural practices and fungicide treatments often are necessary to control blackspot. The first step in controlling blackspot is to select a suitable planting site for roses. Sites that receive full sun and provide good air movement are best for roses. Full sun and good air movement promote drying of the rose foliage and discourage blackspot infections. Reduce the amount of overwintering fungi by carefully cleaning up the leaf debris in fall. When watering roses, apply water directly to the ground around the plants. Do not wet the foliage. Fungicide applications must begin at the first sign of disease symptoms.

Q. Can you recommend climbing rose varieties that perform well in Iowa?

A. Generally, climbing roses don't perform well in Iowa. Many bloom on the previous year's growth, but suffer extensive winter dieback. As a result, many climbing roses bloom little or not at all. The following roses are noted for their hardiness, vigor, and disease resistance.

'William Baffin' produces semi-double, deep pink, 3-inch flowers. The center of each blossom contains bright gold stamens. Plants bloom heavily in June with light to moderate bloom through the summer. 'William Baffin' is an upright plant, which can reach a height of 8 to 9 feet. It can be grown as a large shrub or climber.

The long, arching canes of 'Henry Kelsey' may grow 8 to 10 feet long. It can be grown as a climber or arching shrub. 'Henry Kelsey' produces semi-double, medium red, 3-inch flowers. Golden stamens highlight the center of each blossom. 'Henry Kelsey' blooms heavily in June with light to moderate repeat bloom.

'John Cabot' bears deep rose-pink, semi-double, 3-inch flowers. The blossoms are moderately fragrant. Plants bloom heavily in June with moderate to heavy bloom through the summer. 'John Cabot' can be grown as a spreading shrub or as a climber.